Tunable self-powered n-SrTiO3 photodetectors based on varying CuS-ZnS nanocomposite film (p-CuZnS, p-CuS, and n-ZnS)

The heterojunction photodetector between n-SrTiO 3 (n-STO) and p-CuS-ZnS (p-CZS) is prepared by a simple chemical bath deposition. The p-CZS/n-STO photodetector exhibits excellent self-powered characteristics under 390-nm light illumination, including high photosensitivity (on/off ratio of 300), fast response speed (0.7/94.6 ms), and good wavelength selectivity (410-380 nm). More importantly, the self-powered n-STO photodetectors can be regulated by varying the composition of CZS film (p-CZS, p-CuS, and n-ZnS). All devices exhibit a large open-circuit voltage and show different self-powered behaviors because of the different built-in electric fields. The open-circuit voltages of the CZS/STO, CuS/STO, and ZnS/STO devices are measured to be 0.56, 0.30, and 0.35 V, respectively. This work provides a simple and effective way to fabricate tunable self-powered photodetectors by varying the composition of the nanocomposite film.